Conventionally, in industrial machines and the like, for the purpose of ensuring the safety of workers, a machine is sometimes enclosed with a protective wall, and a protective door for the entry into the inside of the wall provided. Generally, in such a configuration, an interlock switch (or safety switch) for detecting whether or not the protective door is completely closed is provided, and a safety system which does not allow the machine to be driven when the protective door is not completely closed is constructed.
The interlock switch is generally configured to include a switch body and an actuator (for example, a key). The switch body is provided on a protective wall surface surrounding the protective door. The actuator is provided at the protective door in such a manner that when the protective wall is closed, the actuator is inserted into an insertion opening for the actuator provided in the switch body.
When the protective door is closed, the actuator is inserted to actuate an operation unit in the interior of the switch body, such as a cam, and a switch built in the switch body is thereby closed. Power is thereby supplied to the machine, making the machine operable.
On the other hand, when the protective door is opened, the actuator is pulled out of the switch body, and the switch of the switch body is thereby opened. Power supply to the machine is thereby interrupted.
Some such interlock switches are configured such that a first portion including the aforementioned operation unit and a second portion including the switch are separable from each other. With such a configuration, an excessive impact applied to the interlock switch may separate the first portion and the second portion from each other. For instance, with a structure in which the pushing force of the operation unit opens the switch above when the actuator is pulled out, upon the separation between the first portion and the second portion, the aforementioned pushing force will disappear, and the switch will be closed. This results in that power is supplied to the machine even when the protective door is not in a completely closed state, and the safety of workers can no longer be ensured.
Japanese Patent Laying-Open No. 2010-157488 (PTL 1) discloses a safety switch which is configured to be separable into a first portion and a second portion in a manner as above and has a structure in which upon the separation between the first portion and the second portion, a switch operates in an opening direction so that the safety is ensured.